High-Nickel Cathode Material Surface NiO Control for Gas Reduction
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Solution Overview
Problem
High-nickel positive electrode active materials in lithium secondary batteries suffer from increased gas generation and reduced structural stability due to high reactivity and lattice instability, limiting their capacity and performance.
Innovation Solution
A method involving the preparation of a lithium transition metal oxide by mixing a transition metal precursor with a high nickel content and sintering, followed by washing with hot water to form a NiO phase on the particle surface, ensuring a specific EELS analysis ratio of peak intensities at 853 eV and 855.5 eV, thereby reducing surface reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content is increased to achieve high capacity, then battery capacity is improved, but gas generation increases and structural stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a dual-structure where the interior maintains high nickel content (70-90 mol%) for high capacity, while the surface layer (5-20 nm thick) has modified composition with reduced nickel content and added protective elements. This spatial differentiation allows the bulk material to provide high capacity while the surface layer provides structural stability and reduced gas generation.
Solution Approach 2:
The patent creates a composite material structure consisting of a high-nickel lithium composite transition metal oxide core combined with a surface layer containing protective elements (aluminum, magnesium, zinc, or calcium). This composite structure combines the high capacity benefits of high-nickel materials with the structural stability and low reactivity of the protective surface layer, resolving the contradiction between capacity and reliability.
2Quantity of substance
If nickel content is increased to achieve high capacity, then battery capacity is improved, but gas generation increases
Solution Approach 1:
The surface layer with modified composition (reduced nickel content and added protective elements) locally suppresses the harmful gas generation reaction that occurs throughout the bulk material. The protective elements in the surface layer reduce reactivity with the electrolyte, preventing gas generation while maintaining high nickel content in the interior for capacity.
Solution Approach 2:
The patent converts the inherently high reactivity of nickel (which causes gas generation) into a benefit by using controlled surface modification. The surface layer's reduced nickel content and added protective elements transform the harmful high reactivity into a controlled interface that prevents gas generation while preserving the high capacity of the bulk high-nickel material.
3Reliability
If coating or doping is applied to improve structural stability, then structural stability is improved, but uniform improvement on both lattice and surface is difficult to achieve
Solution Approach 1:
The patent segments the modification approach into two distinct parts: a bulk high-nickel phase for capacity and a separate surface layer (5-20 nm thick) for stability. This segmentation allows independent optimization of each region's properties and achieves uniform improvement throughout the material structure, overcoming the limitations of conventional coating or doping methods.
Solution Approach 2:
The patent achieves uniform structural stability by changing key parameters: the surface layer thickness (5-20 nm), the nickel content gradient (from 70-90 mol% in bulk to lower in surface), and the addition of protective elements (Al, Mg, Zn, or Ca) at specific concentrations. These parameter changes ensure uniform stability improvement across the entire material while maintaining manufacturing feasibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enhances structural stability and reduces gas generation and leakage current, improving the battery's capacity and performance under high-voltage and high-temperature conditions.
Implementation Method 1
washing the lithium transition metal oxide with hot water of more than 90° C., wherein, after the second step, a result of EELS analysis of a particle surface of the lithium transition metal oxide satisfies Equation 1
Implementation Method 2
a first step of preparing a lithium transition metal oxide by mixing a lithium raw material and a transition metal precursor containing 70 mol % or more of nickel based on the total number of moles of transition metals and sintering the mixture
Data Source
AI summary
A method of preparing a positive electrode active material for a lithium secondary battery and a positive electrode active material prepared thereby. T the preparation method includes a first step of preparing a lithium transition metal oxide by mixing a lithium raw material and a transition metal precursor containing 70 mol % or more of nickel based on the total number of moles of transition metals and sintering the mixture; and a second step of washing the lithium transition metal oxide with hot water of more than 90° C., wherein, after the second step, a result of EELS analysis of a particle surface of the lithium transition metal oxide satisfies Equation 1.